The Guardian, Friday 30 March 2012 Article history A Soca report warns Home Office that police data is being compromised. Photograph: Clara Molden/PAPrivate investigators linked to organised crime gangs accessed and deleted police intelligence records, according to a leaked report.

A confidential report by the Serious Organised Crime Agency (Soca) in 2008, shown to Channel 4 News, warned the Home Office that private investigators were using corrupt serving and former officers to delete intelligence files from the national police computer and other databases and access details of police operations.

The eight-page report, which is understood to have been passed to the Leveson inquiry, described unauthorised access to details of current investigations, the location of witnesses under police protection, the identity of informants and the provision of counter-surveillance techniques.

The Soca investigation, codenamed Riverside, found examples of corrupt individuals providing access to information in four of five law enforcement operations scrutinised until 2007. As well as police officers, it is claimed, they included a bank employee, employees in a communications service provider, a public service worker, and a prison service employee.

The report added: "The ability of the investigators to commit such criminality is supported by the absence of regulation in the industry, an abundance of law enforcement expertise either through corrupt contacts or from a previous career in law enforcement, easy access to specialist experts and abuse of legally-available technology."

The disclosure is likely to provoke renewed calls for private investigators to be regulated. The then home secretary, Jacqui Smith, is also set to be called before the home affairs select committee to explain whether she was aware of the findings.

Keith Vaz, chairman of the committee, which has lunched an inquiry into private investigators, told Channel 4 News he would ask colleagues to summon Smith and Soca to give evidence. "If they knew that there was this widespread deletion of information, and the connection between private investigators and police officers who were involved in inappropriate action, it's very important that they come before the committee and explain themselves, as a matter of urgency," he said.

A Soca spokesman said it did not comment on "inappropriately obtained" reports. A Home Office spokesman said it was "considering whether to regulate private investigators".

Other unlawful activities uncovered included accessing serving police officers' private details and the identity of vehicles used in surveillance, as well as checks on what police interest there was in particular criminal outfits.

The former head of anti-corruption at the Met Police, Bob Quick, told the programme: "There were occasions where cases involved officers removing evidence, destroying evidence.

"This was infrequent but when it occurred it was serious. There were indications that relationships existed with private investigators and ex-police officers who were suspected of corruption."